Reactive, non-yellowing triazine compounds useful as UV screening agents for polymers

ABSTRACT

Triazine compounds are disclosed which are useful for imparting UV screening properties to polymers of the formula: ##STR1## wherein R is an electron withdrawing group; R 1  is H, ##STR2## where R 3  is an alkyl group having from one to about six carbon atoms; and R 2  is selected from H and CH 3 , also disclosed are polymer compositions having improved UV screening properties containing said triazine compounds.

The present invention relates to triazine compounds useful for impartingUV (ultraviolet) screening properties to polymers. More particularly,the present invention relates to non-yellowing triazine compounds andpolymer compositions.

Many products such as fruit juices, soft drinks, drinks, food products,cosmetics and shampoos are deleteriously affected by UV light whenpackaged in clear plastic containers which pass significant portions ofthe available light at any wavelength from approximately 300 to 400 nm.By use of the triazine compounds of the present invention polymericcontainers may be manufactured which absorb these harmful wavelengthsand therefore reduce or eliminate the UV light degradation of productspackaged therein.

The triazine compounds of the present invention may also be useful forproviding UV screening properties in films and coatings, especiallycoatings to be used for outdoor applications such as automobiles,aircraft, buildings, etc.

Commercially available UV stabilizers for coatings may tend to diffuseout of the coating or become extracted from the coating by, forinstance, detergents or solvents. Because such coatings, however, arecrosslinked using conventional crosslinking agents, it has been foundthat the present triazine compounds may react with the crosslinkingmaterials thus becoming permanently bonded to the coating. Because theyare bonded to the coating, they may be nonextractable and less subjectto diffusion out of the coating.

The present triazine compounds are thermally stable and generallynonsublimable at the processing temperatures normally encountered forthe application end uses described above, e.g., films, coatings andbeverage and food containers.

A further advantage of the present triazine compounds is that they mayimpart UV stabilization to the conventional additives used in food andbeverage containers and bottles and in films and coatings, such ascolorants, pigments, fillers, brighteners and the like.

The triazine compounds of the present invention offer the furtheradvantage of being relatively non-yellowing as compared to knowntriazine compounds of the type, for instance, disclosed in U.S. Pat.Nos. 3,244,708 (Ciba-Geigy) and 4,619,956 (American Cyanamid) and inEuropean Patent Application No. 165,608 (Ciba-Geigy). The presenttriazine compounds, furthermore, may be relatively non-yellowing both ina pure (nonreacted) and reacted form.

In accordance with the present invention, certain triazine compoundsdefined below are provided, said compounds having the formula: ##STR3##wherein R is an electron withdrawing group; R₁ is H ##STR4## where R₃ isan alkyl group having from one to six carbon atoms; and R₂ is selectedfrom H and CH₃. Preferably the electron withdrawing groups selected forthe R position may include halogen, cyano, trifluoromethyl, nitro, andacetoxy. Even more preferably R is halogen, eg, chlorine, bromine andfluorine.

Also contemplated by the present invention is a polymer compositionwhich comprises a polymer having reacted therein a total of from about0.05 to about 5, preferably from about 0.1 to about 2 percent by weightbased upon the weight of the polymers of at least one UV absorbingcompound of the formula: ##STR5##

As mentioned above, the polymers which may be stabilized against thedeleterious effects of UV light according to the present inventioninclude a wide range of polymers made by condensation reactions andaddition reactions. Polymers made by condensation reaction may include,for instance, alkyds, the aminos, e.g., melamine and urea, epoxies,phenolics, polycarbonates, polyesters, and silicones. With regard tosuch condensation polymers the triazines may be reacted therewiththrough a reactive hydroxyl group on the triazine compound or thereaction may be through a reactive ester group on the triazine by meansof a transesterification reaction.

Particularly preferred condensation polymers include linear,thermoplastic molding polymers such as polyesters, copolyether esters(such as Hytrel® made by DuPont) and polycarbonates. Polyester, fibergrade polymers may also be preferred.

Suitable polymers made by addition reaction include, for instance,polyurethanes and epoxy resins.

The triazine compounds of the present invention may also havesignificant applications as a UV screening agent for coatings,especially exterior coatings where degradation of the coating due to UVexposure may be a problem. In this application area the triazinecompound also becomes bound and may be, hence, non-sublimable andnon-extractable. In the case of cured coatings, such as reactiveacrylics cross-linked with melamine-formaldehyde, urea-formaldehyde orisocyanates, the triazine compounds may become bonded to the coatingduring crosslinking where the compounds react with the crosslinkingagents conventionally employed in such coatings. In two-part urethanecoatings, where an isocyanate is reacting with a polyol or polyamine toform the final polymeric coating, the triazine becomes bound into thefinal polymer through reaction with the isocyanate. In the case of othercoating systems, such as alkyds and unsaturated polyesters, the triazinecompounds are bonded into the polymer during the original polymerizationstep and the polymers are then cured conventionally by a free radicalmechanism.

As to the non-yellowing feature of the compounds of the presentinvention, it will be apparent to those skilled in the art that such afeature may be particularly advantageous where yellowing of the productcannot be tolerated. Why the compounds of the present invention exhibitthis non-yellowing feature is not fully understood. However, while notbeing limited to any particular theory, it is theorized that the presenttriazines may be non-yellowing due to the presence of theelectron-withdrawing group on the phenyl ring (ring A in the structure)of the triazine molecule. Substitution on the ortho or para position ofring A may be preferred. Most preferred is the para position.

The electron withdrawing group, it is theorized, may reduce the basicityof the triazine molecule which may render it less susceptible todegradation and resultant yellowing.

The present invention may be further understood by reference to thefollowing examples which are not to be construed as limiting the scopeof the subject matter of the invention in any way. Unless otherwiseindicated all parts or percentages are by weight.

EXAMPLE 1 Synthesis of2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)-phenyl]-6-(4-chlorophenyl)-1,3,5-triazine

A slurry of cyanuric chloride (500 g, 2.71 mol) and aluminum chloride(800 g, 6.01 mol) in chlorobenzene (2.4 L) was maintained at 125° C. for18 hours under nitrogen. The mixture was cooled to room temperature andthen poured into ice water (4 L). A steam distillation of the quenchedreaction mixture removed chlorobenzene. The crude product was collectedby filtration and dried. The crude product identified below wasrecrystallized from acetonitrile: mp 149°-150° C.

2,4-dichloro-6-(4-chlorophenyl)-1,3,5-triazine (I)

A slurry of compound I (425gg, 1.64 mol) and resorcinol (365 g, 3.31mol) in nitrobenzene (2.4 L) was cooled to 10° C. under nitrogen. Then,with efficient cooling, aluminum chloride (500 g, 3.75 mol) was addedover 1 hour. The slurry was allowed to warm up to room temperature andstir for 16 hours, followed by heating for 4 hours at 50° C. Aftercooling to room temperature, the mixture was poured into ice water (4 L)containing HC1 (100 mL). Next, the slurry was washed with water until pH2. A steam distillation of the washed slurry removed nitrobenzene. Thecrude product was collected by filtration and dried. The crude productidentified below was recrystallized from N,N-dimethylformamide-water:mp>300° C.

2,4-bis(2,4-dihydroxyphenyl)-6-(4-chlorophenyl)-1,3,5-triazine (II)

A slurry of compound II (100 g, 0.25 mol) in ethoxyethanol (750 mL) waswarmed to 40° C. Then, potassium carbonate (40 g, 0.29 mol) was addedand the mixture was heated to reflux under nitrogen. Next,2-chloroethanol (80 mL, 1.19 mol) was added dropwise over 12 hours. Anadditional quantity of potassium carbonate (40 g, 0.26 mol) was added inseveral portions to maintain a pH of 9 throughout the 2-chloroethanoladdition. The mixture was cooled to room temperature and the precipitatethat formed was collected by filtration. The crude product was washedwith water, collected by filtration and dried. The crude productidentified below was recrystallized from 1,4-dioxane: mp 232°-234° C.;UV-absorption (ethyl benzoate) λ_(max) =359 nm, *E_(max) =74. Analysiscalculated for C₂₅ H₂₂ C1N₃ O₆ : C, 60.55; H, 4.47; C1, 7.15; N, 8.47;0, 19.36. Found: C, 60.30; H, 4.59; C1, 6.91; N, 8.44; 0, 19.55.

2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)-phenyl]-6-(4chlorophenyl)-1,3,5-triazine(III) EXAMPLE 2 Preparation Of The Corresponding Ester

A slurry of compound III (10 g, 0.02 mol) and p-toluenesulfonic acid(0.3 g, 0.002 mol) in acetic anhydride (100 mL) was heated undernitrogen up to 70° C. in 15 minutes. When the slurry dissolved, thesolution was cooled to room temperature. Then, the mixture was quenchedin pH 9 water. The precipitate was collected by filtration and dried.The crude product identified below was recrystallized from ethylacetate: mp 138°-140° C.; UV-absorption (N,N-dimethylformamide) λ_(max)=352 nm, *E_(max) =62. Analysis calculated for C₂₉ H₂₆ C1N₃ O₈ :C,60.05; H, 4.52; C1, 6.11; N, 7.24; 0, 22.06. Found: C, 60.08; H, 4.51;Cl, 7.17; N, 7.06; 0, 21.41.

2,4-bis[2-hydroxy-4-(2-acetoxyethoxy)-phenyl]-6-(4-chlorophenyl)-1,3,5-triazine(IV) EXAMPLE 3 Comparative Example

A dry reactor under nitrogen was charged with tetrahydrofuran (500 mL)and cyanuric chloride (90 g, 0.49 mol). Then, 2M phenyl magnesiumchloride in tetrahydrofuran (275 mL) was slowly added over 4 hours. Themixture was warmed to 40° C. and was left to stir overnight. Thetetrahydrofuran was then removed by vacuum distillation. To theremaining mixture was added nitrobenzene (500 mL) and resorcinol (78 g,0.71 mol). The mixture was cooled to 10° C. Then, with efficientcooling, aluminum chloride (100 g, 0.75 mol) was added over 30 minutes.The mixture was then heated for 24 hours at 50° C. After cooling to roomtemperature, the mixture was poured into ice water (4 L) containing HC1(100 mL). Next, the slurry was washed with water until pH 2. A steamdistillation of the washed slurry removed nitrobenzene. The crudeproduct identified below was collected by filtration and dried.

2,4-bis(2,4-dihydroxyphenyl)- 6-phenyl-1,3,5-triazine (V)

A slurry of compound V (100 g, 0.27 mol) in ethoxyethanol (750 mL) waswarmed to 40° C. Then, potassium carbonate (40 g, 0.29 mol) was addedand the mixture was heated to reflux under nitrogen. Next,2-chloroethanol (100 mL, 1.49 mol) was added dropwise over 12 hours. Anadditional quantity of potassium carbonate (60 g, 0.43 mol) was added inseveral portions to maintain a pH of 9 throughout the 2-chloroethanoladdition. The mixture was cooled to room temperature and the precipitatethat formed was collected by filtration. The crude product was washedwith water, collected by filtration and dried. The crude productidentified below was recrystallized from 1,4-dioxane: mp 250°-252° C.;UV-absorption (ethyl benzoate) λ_(max) =358 nm, *E_(max) =78. Analysiscalculated for C₂₅ H₂₃ N₃ O₆ : C, 65.07; H, 5.02; N, 9.11; 0, 20.80.Found: C, 64.93; H, 5.09; N, 9.03; 0, 21.30.

2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)-phenyl]-6-phenyl-1,3,5-triazine(VI) EXAMPLE 4 Comparative Example

A slurry of cyanuric chloride (80 g, 0.43 mol), m-xylene (60 mL, 0.49mol), and aluminum chloride (100 g, 0.75 mol) in chlorobenzene (500 mL)was stirred under a nitrogen blanket. Next, the slurry was maintained at40° C. for 4 hours, followed by cooling to room temperature overnight.The slurry was poured into hexanes (1.5 L). The hexanes layer wasdecanted away from a black oil. Next, ice water (3 L) was added to theblack oil resulting in a white precipitate. The crude product identifiedbelow was collected by filtration. It was washed with acetone (500 mL).

2,4-dichloro-6-(2,4-dimethylphenyl)-1,3,5-triazine (VII)

A slurry of compound VII (138 g, 0.55 mol) and resorcinol (120 g, 1.10mol) in nitrobenzene (1 L) was cooled to 10° C. under nitrogen. Then,with efficient cooling, aluminum chloride (250 g, 1.88 mol) was addedover 30 minutes. The slurry was allowed to warm up to room temperatureand stir for 16 hours. The mixture was poured into ice water (4 L)containing HC1 (100 mL). Next, the slurry was washed with water until pH2. The crude product was collected by filtration and then washed inhexanes. The crude product was collected again by filtration and dried.The crude product identified below was recrystallized fromN,N-dimethylformamide-water. mp>300° C.

2,4-bis(2,4-dihydroxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine(VIII)

A slurry of compound VIII (50 g, 0.12 mol) in ethoxyethanol (400 mL) waswarmed to 40° C. Then, potassium carbonate (20 g, 0.14 mol) was addedand the mixture was heated to reflux under nitrogen. Next,2-chloroethanol (30 mL, 0.45 mol) was added dropwise over 12 hours. Anadditional quantity of potassium carbonate (7 g, 0.05 mol) was added inseveral portions to maintain a pH of 9 throughout the 2-chloroethanoladdition. The mixture was cooled to room temperature and the precipitatethat formed was collected by filtration. The crude product was washedwith water, collected by filtration and dried. The crude productidentified below was recrystallized from methyl ethyl ketone: mp204°-207° C.; UV-absorption (N-N-dimethylformamide) λ_(max) =351 nm,*E_(max) =84. Analysis calculated for C₂₇ H₂₇ N₃ O₆ : C, 66.25; H, 5.56;N, 8.58; 0, 19.60. Found: C, 66.14; H, 5.59; N, 8.46; 0, 19.78.

2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)-phenyl]-6-(2,4-dimethylphenyl)-1,3,5-triazine (IX) EXAMPLE 5

A slurry of cyanuric chloride (100 g, 0.54 mol) and aluminum chloride(175 g, 1.31 mol) in bromobenzene (450 mL) was maintained at 120° C. for24 hours under nitrogen. The mixture was cooled to room temperature andthen poured into ice water (2 L). A steam distillation of the quenchedreaction mixture removed bromobenzene. The crude product was collectedby filtration and dried. The dried crude product identified below wasrecrystallized from acetonitrile: mp 161°-163° C.

2,4-dichloro-6-(4-bromophenyl)-1,3,5-triazine (X)

A slurry of compound X (74 g, 0.25 mol) and resorcinol (60 g, 0.55 mol)in nitrobenzene (500 mL) was cooled to 10° C. under nitrogen. Then, withefficient cooling, aluminum chloride (125 g, 0.94 mol) was added over 30minutes. The slurry was allowed to warm up to room temperature and stirfor 16 hours, followed by heating for 4 hours at 50° C. After cooling toroom temperature, the mixture was poured into ice water (3 L) containingHC1 (50 mL). Next, the slurry was washed with water until pH 2. A steamdistillation of the washed slurry removed nitrobenzene. The crudeproduct was collected by filtration and dried. The crude product wasrecrystallized from N,N-dimethylformamide-water: mp>300° C.

2,4-bis(2,4-dihydroxyphenyl)-6-(4-bromophenyl)-1,3,5-triazine (XI)

A slurry of compound XI (55 g, 0.12 mol) in ethoxyethanol (400 mL) waswarmed to 90° C. Then, potassium carbonate (20 g, 0.15 mol) was addedand the mixture was heated to reflux under nitrogen. Next,2-chloroethanol (42 mL, 0.63 mol) was added dropwise over 12 hours. Anadditional quantity of potassium carbonate (22 g, 0.16 mol) was added inseveral portions to maintain a pH of 9 throughout the 2-chloroethanoladdition. The mixture was cooled to room temperature and the precipitatethat formed was collected by filtration. The crude product was washedwith water, collected by filtration and dried. The crude productidentified below was recrystallized from 1,4-dioxane-acetone: mp222°-224° C.; UV-absorption (N,N-dimethylformamide) λ_(max) =352.5 nm,*E_(max) =66. Analysis calculated for C₂₅ H₂₂ BrN₃ O₆ : C, 55.56; H,4.10; Br, 14.78; N, 7.77; 0, 17.76. Found: C, 55.44; H 4.14; Br, 14.14;N, 7.64; 0, 18.81.

2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)-phenyl]-6-(4-bromophenyl)-1,3,5-triazine (XII) EXAMPLE 6 The Non-Yellowing Characteristic of SolidCompound III versus Other Mixed Triazine Compounds.

One gram of Compounds II, III, VI, IX, and XII were each separatelyslurried in aliquots of boiling ethoxyethanol(25 mL). Each slurry wascoated while hot on stainless steel plates. The ethoxyethanol wasallowed to evaporate into the air. The resulting coatings wereapproximately 4 mil thick.

The plates were the exposed in the Hanau Xenotest 1200 for 48 hours at63° C. and 50% relative humidity. The change in color was measured by aHunter Lab-Scan II Color Difference Meter. The color difference observedrepresents a change in yellow and is denoted by the symbol Δb.

                  TABLE I                                                         ______________________________________                                        Yellowing of Pure Triazines Upon                                              Exposure to UV-Light in Accelerated Weathering                                UV-              Hours of                                                     Absorber         Exposure Δb                                            ______________________________________                                        Compound II      48       +1.8                                                Compound III     48       -0.2                                                Compound VI      48       +5.3                                                Compound IX      48       +11.5                                               Compound XII     48       -0.3                                                ______________________________________                                    

EXAMPLE 7 Preparation of Poly(ethylene terephthalate) ContainingUV-Absorber

For the preparation of poly(ethylene terephthalate) reacted withCompound III, the following chemicals are placed in a flask:

    ______________________________________                                        dimethyl terephthalate                                                                         97.0          parts                                          ethylene glycol  62.0          parts                                          metal catalyst   0.04          part                                           ______________________________________                                    

The flask is equipped with a nitrogen inlet, stirrer, vacuum outlet, andcondenser. The flask and contents are heated slowly to 210° C. at whichtime 0.01 part of phosphorous catalyst is added. When the temperaturereaches 230° C. 0.5 part of Compound III is added to the flask. Next,the pressure is reduced and the temperature increased until the vacuumis 0.02 mm Hg and temperature is 285° C. The polymer condensation iscomplete within 1 hour at these conditions. When the flask is cooled;the resulting polymer is clear yellow. An experiment of this typeresulted in a polymer which when molded into a film absorbed UV-lightbetween 250-400 nm. It was also found that addition of Compound III didnot affect the kinetics of the polymer condensation, nor did it sublimeout of or discolor the poly(ethylene terephthalate) resin significantly.

EXAMPLE 8 Preparation of Coatings Containing UV-Absorbers

An extraction study was carried out on crosslinked acrylic enamelscontaining Compound III and competitive UV-absorbers to determine ifthey were extractable. Stock solutions of Compound III, Tinuvin 900¹,Tinuvin 1130², and 2-(2H-benzotriazol-2-yl)-5-methoxyphenol were made bydissolving the UV-absorber (0.3 g) in N,N-dimethylformamide (10 mL). Thesamples were made by adding 1 mL aliquots from each stock solution toseparate portions of Acryloid AT-51³ (4 g). The resin samples wereplaced in separate aluminum weighing dishes and allowed to air dry for 2hours. They were then cured at 120° C. for 3 hours producing a hardenamel. After cooling to room temperature, the samples were broken intosmall pieces and soaked in N,N-dimethylformamide for two days. HighPressure Liquid Chromatography analysis of the N,N-dimethylformamidesolutions indicated that Tinuvin 900¹ and2-(2H-benzotriazol-2-yl)-5-methoxyphenol were extracted from thesamples, but Compound III and Tinuvin 1130² were not extracted.Evidently, the primary aliphatic hydroxy substituents on Compound IIIand Tinuvin 1130² react with the hydroxymethyl melamine crosslinker,binding the stabilizer to the enamel.

Footnotes EXAMPLE 9 The Non-Yellowing Characteristics of a CoatingContaining Bound Compound III versus Coatings Containing Other BoundTriazine Compounds

A yellowing study was carried out on coatings containing Compound IIIand other reactive triazine compounds. Stock solutions of Compound III,Compound VI, and Compound IX were made by dissolving 0.6 grams of eachcompound in N,N-dimethylformamide (100 mL). Three coating resins weremade by adding 5 mL of stock solution to 6 grams of Acryloid AT-51³coating resin. A fourth coating resin was made by adding 5 mL N,N-dimethylformamide to 6 grams Acryloid AT-51³ resin. Aliquots of 6grams from each coating resin were cast as coatings onto white ceramictiles using a #20 drawdown rod. The coatings were cured at 120° C.overnight. The coatings were placed in the Hanau Xenotest 1200 at 63° C.and 50% relative humidity. The color change was measured at intervalsusing a Hunter Labscan II Color Difference Meter. The color differenceobserved represents a change in yellow and is denoted by the symbol Δb.The values for Δb are listed in Table 2.

                  TABLE 2                                                         ______________________________________                                        Yellowing of Coatings Containing UV-Absorbers                                 Upon Exposure to UV-Light in Accelerated Weathering                           UV-               Hours Of                                                    Absorber          Exposure Δb                                           ______________________________________                                        Compound III      238      0.0                                                No Stabilizer     238      0.2                                                Compound VI       238      0.6                                                Compound IX       238      0.3                                                ______________________________________                                    

EXAMPLE 10 Extraction Study of Poly(ethylene terephthalate) ResinContaining UV-Absorber

Poly(ethylene terephthalate) resins containing 5000 and 7500 ppm ofCompound III were prepared in a similar manner to that described inExample 7. Exactly 0.2 grams of each batch of the resin was mixed withspectroscopy grade N,N-dimethylformamide (100 mL) for 15 minutes at 100°C. Analysis of the liquid extract by High Pressure Liquid Chromatographyand UV spectroscopy showed that no significant amount of Compound IIIwas present in the extract. Samples were extracted in duplicate andspiked for confirmation.

We claim:
 1. A triazine compound useful for imparting UV screeningproperties which is represented by the formula: ##STR6## wherein R isselected from chlorine, bromine, fluorine, R¹ is H, ##STR7## where R₃ isan alkyl group having from one to 6 carbon atoms; and R₂ is selectedfrom H and CH₃.